Productivity Determination and Pump Resizing Using Variable-Speed Electric Submersible Pumps

Abstract

This paper discusses a variable-speed electric submersible pump system usedas a tool to provide productivity information for resizing electricsubmersible pumps. Use of this equipment enabled the generation ofproductivity information without having to pull the existing downholeequipment. Field results using this method are presented. Introduction Waterflood expansion and developmental drillingprograms are being pursued actively in the LostSoldier Tensleep reservoir in central Wyoming. Response to the increased injection has resulted infrequent resizing to larger artificial lift equipment.As new injection wells are drilled and existing wellsconverted to injection to complete the pattern flood, adjacent areas are experiencing significant increasesin static and operating bottomhole pressures. Tohandle the increased fluid withdrawals possible, themajority of producing wells are being changed frombeam to electric submersible pump (ESP) lift andexisting ESP's are being resized. The production of ESP-pumped wells in the LostSoldier Tensleep reservoir ranges from 400 to 6,200BFPD (64 to 986 m3/d fluid). Average depth of the reservoir is 5,000 ft (1524 m). Producing-wellbottomhole temperature is approximately 175 degreesF (79 degrees C).ESP lift plays an important role in this reservoir.At the end of 1978, 31 well, or 61% of all producing wells, were on ESP lift. These wells account for 87%of the total fluid produced. During the year therewere 10 new ESP installations and 14 ESP installationsthat were resized. It has been found thattraditional methods of predicting productivitycharacteristics for ESP sizing cannot be used in allcases. Several different size installations have beenrequired in some wells before an acceptable operatingfluid level has been achieved. As a solution to reducing the uncertainty in sizingESP's, a variable-speed electric submersible pump(VSESP) was employed. By varying the frequency tothe downhole motor, it is possible to increase fluidproduction without pulling the existing downholeequipment. This paper discusses the results obtainedby using this equipment on two Lost Soldier Tensleepwells. Resizing still will be necessary as response toinjection is seen in certain areas. However, once it hasbeen determined that a resize is justifiedeconomically, the VSESP can be used as a tool to aidwith sizing for the existing conditions. Otherapplications for this equipment also exist. A thirdwell tested is discussed briefly because it resulted in a further application. JPT P. 1503＾